This is the case, for example, of so-called blade harvesting machines, of the type described in the patent U.S. Pat. No. 4,204,386. The use of machines of this type allows, also in the case of large surface areas, the execution of the harvesting operations in relatively short periods of time with a considerable reduction in costs; on the other hand, this system of harvesting damages considerably the integral nature of the vegetables which, in terms of appearance and quality, are substandard and therefore can be sold only at prices which are unsatisfactory or even, as mentioned further above, may not even be suitable for sale.
Other solutions which are available today, although partially solving the problems posed by the machines of the type described above in that they ensure an end product of acceptable quality, restrict considerably both the range of vegetables which can be cultivated and the type of operations which can be performed.
For example, cultivation methods of the type schematically shown in FIGS. 6a and 6b are known; said systems envisage, in particular, the transplanting the young plants or seedlings 5 through a film 8 of plastic or cellophane spread beforehand over the cultivation bed; the “clodded” seedlings 5, i.e. with clods of earth around the root system, are planted (see FIG. 6b) by perforating the plastic film 8 so as to allow, during the vegetative cycle, the growth of the leafy body above the film 8 (see FIG. 6a).
The harvesting of the fully grown vegetables is performed by performing in sequence cutting of the roots and retrieval of the film so that the seedlings, imprisoned by the film, are raised from the ground and, once separated from the film, may be arranged in special containers which are in turn despatched for distribution.
The system of harvesting described above allows mechanised harvesting but involves, on the other hand, major drawbacks; for example, sowing may be performed only by means of transplanting of the clodded seedlings, whereas sowing by means of scattering of the seeds is not possible owing to the presence of the plastic film. Moreover, the application of the abovementioned harvesting system for vegetables other than lettuce is not known, while the cultivation of spinach which involves sowing by means of scattering of the seeds is not possible; also, it is not possible to vary, even minimally, the sequence of operations associated with sowing, not even in particular environmental conditions (persistent rain, etc.). In fact, spreading of the film may be performed only in sequence with and at the same time as sowing, such that the versatility of operation is very much limited.
Finally, the high cost of the plastic film and the fairly slow rate of seedling transplantation (4000-5000 clods/hour) increase considerably the cultivation costs.